Natural selection sidelined by medical science?
This first possibility assumes that failure of an individual to reach reproductive age and then actually give rise to offspring is the major evolutionary force. In nature, natural selection is the most powerful evolutionary force, but other factors may take over, in a sense, when technology grants a second chance to those who would have died in the wild. Consequently, even a complete lack of natural selection doesn’t mean that humans will not evolve.
Charles Darwin in his book proposed natural selection as the mechanism by which evolution operates. Natural selection is often explained as ‘survival of the fittest’. Those individuals that are born with traits that best enhance survival to maturity are more likely to grow up and reproduce compared with individuals lacking such traits. Another way of saying this is: fitter individuals out-compete those that are less fit to survive in a particular environment. When an individual leaves offspring, its traits are passed down in genes to a new generation.
Darwin did not know about genes, but careful, detailed observations during his famous voyage on the Beagle led him to make observations of phenomena that were consistent with the idea that traits somehow were transferred from generation to generation. One observation that Darwin made was that in each generation more offspring were born than could possibly survive. In nature, many that are born to parents simply do not survive to maturity, but this was also a reality for humanity until very recently. Particularly in urban areas, such as New York City, where immigrants were arriving in droves. Couples had many children intentionally, expecting that some would die of diphtheria, measles, polio –any one of a plethora of communicable diseases.
This was a typical way that people used to die, but did their deaths lead the survivors to evolve some resistance to these diseases through natural selection? It’s hard to know because within a generation or two there were vaccines for all of these diseases, so the population was immunized artificially.
A similar phenomenon emerges if we consider purification of public water supplies and antibiotics, drugs that kill bacteria. Most of the medical conditions that used to kill high numbers of babies, children, teens, and young adults as recently as a century ago are either prevented or cured today. Furthermore, children who are born with major disabilities, such as missing limbs, can today grow to adulthood and reproduce in a world where technology for prosthetic limbs is developing rapidly.
Can one measure a lack of evolution? That is hard to do over the span of the few generations during which modern science has been operating, but it may be possible in the future. One strategy might be to monitor changes in sequences of human genes vital to immunity and disease, intelligence, athletic fitness, and other traits, then compare the rates of change with similar genes in species that live in the wild.
Artificial selection is the selective breeding of animals or plants by humans to modify an organism. Genetic drift is a change in the frequency of a population's genes and alleles over time, often by founder effects (when a small group of individuals relocate) or bottlenecking (when a large population is decimated, leaving a smaller group to repopulate).
When a portion of a population is separated, like when settlers leave for a new location - a type of genetic drift called the founder effect occurs. The separated population's genetic makeup starts to change and, over time, match that of the founding men and women.
When a catastrophic event kills off a large portion of a population and a small group of survivors is left to repopulate, it is a type of genetic drift known as the bottleneck effect. It results in a smaller gene pool and a different mix of allele frequencies.
Transhumanism: shaping our evolution through technology
Transhumanism is the idea that humans can evolve new physical and mental capabilities, particularly through the use of science and engineering. In a literal sense, all of us are transhumans already, because we’ve extended our natural capabilities with technology. This began with simple inventions like clothing in Stone Age times, but you can extend that to people today walking around with artificial valves and pacemakers in their hearts and implanted pumps that infuse them with drugs, such as insulin. The concept can be extended to include communication equipment that we wear, such as smartphones, or vehicles that we enter, such as cars and aircraft. Biotechnology is developing at an ever-increasing rate. Bionic limbs are being tested, arms and legs that a wearer can control via thoughts from his or her brain. Biomedical devices are becoming more dependent on computing capability, improvement of which has followed the so-called Moore’s Law, proposed by the founder of Intel Corporation, who suggested that computing power doubles roughly every 18-24 months.
There may be a theoretical limit to computing power, but it is at least a few decades before we reach it. Along with sheer computing power, developments such as nanotechnology, new genetic engineering methods, and integration of biological and electronic technology will add to what is possible. Thus, at some point in the decades to come, we can expect various technologies that today seem like science fiction, such as a bionic artificial heart that can replace a diseased heart and run indefinitely. Or maybe we will develop the ability to grow a genetically-matched human heart in a host animal such as a pig or sheep.
One day the human genome could be altered in a heritable way with a DNA editing system called CRISPR.
An illustration of gene drive, where a trait is spread to other members of the same species.
Durdanto
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